In oil fired boilers, furnaces and the like, atomizers are commonly used to disperse the oil as a fine mist into the combustion chamber prior to firing. These atomizers serve the purpose of exposing as much oil particle surface as possible for contact with the combustion air in order to insure prompt ignition and burning.
Additionally, atomizers are used in downstream contaminant removal processes. For example, in a dry or semi-dry flue gas desulfurization process, a liquid or slurry reagent and/or recycle by-product is sprayed onto the incoming flue gas to remove sulfur or other contaminants before the flue gas is released to the atmosphere. In such a process, the liquid or slurry or reagent and/or recycle by-product is atomized for greater contact between the sprayed product and the contaminant to be removed.
Several methods of atomizing currently exist; some use steam or air to atomize while others use mechanical means to achieve the desired result. Steam or air atomizers operate on the principle of producing a steam-fuel (or an air-fuel) emulsion which, when released into the combustion chamber, atomizes the oil through the rapid expansion of the steam or air. Mechanical atomizers operate by using the pressure of the fuel itself as the means of atomization. While some mechanical atomizers have moving parts close to the furnace opening, these have generally lost favor due to their higher maintenance needs.
Despite the type used, it has been found desirable to surround the atomized mist (whether it be oil used in furnaces or boilers or a slurry of reagent and/or recycle by-product used in downstream contaminant removal processes) with a shield gas (normally air) as this mist enters the furnace or scrubber enclosure. In furnaces, this shield gas insures a local source of combustion air. In both furnaces and downstream contaminant removal processes, the shield gas maintains (or shields) the spray so that its direction will not be interrupted or deflected due to the currents within the furnace or scrubber vessel enclosure. Additionally, the shield gas minimizes or prevents any deposit of the liquid/solids emitted by the atomizer from developing on the surface of the atomizer head.
In the past, such shield gas was supplied by positioning the atomizer head concentrically inside a conduit thereby creating an annular flow area around this head which directed the shield gas to the tip of the atomizer head. While this method would seem to function sufficiently, it provides a single relatively large annular gas flow path that surrounds the entire atomizer head rather than the individual exit orifices on the atomizer head. Thus, while the outer exit orifices on the periphery of the atomizer head will have immediate access to the surrounding shield gas, the interior exit orifices will not be so fortunate since they are located some distance from this shield gas. Additionally, should the atomizer head be configured solely with outer exit orifices, the above arrangement would still only supply shield gas around the outer region of the spray coming from the atomizer head, it would not surround each individual spray from each individual exit orifice.
It is thus an object of this invention to provide a supply of shield gas that will surround each exit orifice of the atomizer head. Another object of this invention is to provide such shield gas in such a manner that it is equally dispersed among the various exit orifices such that no one orifice receives a greater supply of shield gas than another. Yet another object of this invention is to provide individual supplies of shield gas around the circumference of the individual exit orifices. These and other objects and advantages of this invention will become obvious upon further investigation.